Gear cutting machine



Sept. 2, 1947. F. JURY GEAR CUTTING mcams Onginal Filed Oct. 25, 1939 4Sheets-Sheet 1 INVENTOR. fiP/w/r W dupl Sept. 2, 1947.

F w. "JURY GEAR CUTTING j MACHINE originai Filed Oct. 25, 1939 4 Sheets-.-Sheet; 2

INVENTOR. fiPA/v/r W z/am ATTORNEY.

Sept. 2, 1947. F. W.'JURY GEAR CUTTING MACHINE Original Filed oct. 2 5,19's9 4 Sheets-{Sheet 3 llllllllll IllllllllllllllllllllllIlllllllllllllllllllillllllIIIH Illllllllll llllllllllllllIllllllllllllllllllllllllillllllll INVENTOR.

[VP/4N 14/ (fa/w ATTORNEY.-

Fill-III! Sept. 2, 19 47. I

F. vfv. U 2,426,774 GEAR CUTTING MACHINE Original' Filed 0012525, 1939 4Sheets-Sheet 4 TTORNEY.

Patented Sept. 2, 1947 UNITED STATES PATENT OFFICE CUTTING MACHINE IFrank W. Jury, Milwaukee, Wis.

Continuation of application Serial No. 301,100.,

October 25, 1939.

This application November 25, 1943, Serial No. 511,673

11 Claims. 1

This invention relates to a gear cutting machine and to the method ofcutting gears.

This application is a continuation of my prior application for gearcutting machine and method of cutting gears Serial No. 301,100 filedOctober 25, 1939.

Objects of this invention are to provide -a novel form of machine and anovel method of cutting substantially circular teeth in a continuousmanner and imparting continuous uniform rotation to the gear blank andcontinuous uniform rotation to the cutter, and at the same timeimparting to the cutter a continuous bodily movement so that thesubstantially circular gear teeth are generated teeth and arecompletely, finished after the cutter has made one complete travel fromone side of the gear blank to the other side of the gear blank.

Further objects are to provide a simple type of gear cutting machine forcutting substantially circular teeth which is rapid in its operation anddoes not require the sudden stopping or starting of any part of themachine, but in which the cutting progresses in a continuous,uninterrupted manner from the beginning to the completion of the cuttingoperation for all of the teeth of the gear Further objects are toprovide a gear cutting machine and a method of cutting gears by means ofcutter teeth whose cutting faces are straight, the teeth themselvesbeing generated by the relative motion of the parts.

Further objects are to provide a gear cutting machine in which the rateof feed or rate of cutting can be adjusted to suit the particular speedof cutting to the particular material that is used :in the gear blank,so that the speed of operation of the machine is limited solely by thesurface speed of cutting, as in a lathe or planer, or any other machineof this type.

It is to be noted that in this machine the blank is rotatingcontinuously while the cutter continuously rotates and simultaneouslytravels bodily from one side of the gear blank to the other, forexample, from below the gear blank to above the gear blank, while thegear blank rotates continuously about a horizontal axis. It is apparentthat the teeth will depart slightly from a circular shape for tworeasons: one, that the upward bodily travel of the cutter while it isrotating and the downward travel of the adjacent face of the blank causethe teeth to deviate slightly from a circular shape, and also because ofthe fact that the circular cutter has a slight upward component on oneside of the gear blank and a slight downward component on the other sideof the blank V 2 due to the rotation of the cutter and the simultaneousrotation of the gear blank, and thus there is a little greater rate oftravel between the gear blank and a cutter tooth on one side than on theother.

This invention, however, has for its furt er object the cutting ofcomplementary teeth on the two gears which are to mesh so that thisdeviation from a circular (shape is accurately compensated for byforming the teeth of the meshing gears with complementary curves.

Therefore, a further object of the invention is to provide means forreversing the relative 'direction of rotation of the cutter and gearblank for the second .gear to thereby cause the teeth of the second gearto mesh accurately with and to be complementary of the teeth of thefirst gear.

Further objects are to provide a machine for cutting substantiallycircular teeth on gears, while the gear blank and cutter arecontinuously rotating and while the cutter is advancing in a planeparallel to the axis of rotation of the gear blank, and to provide meansincluding change gear mechanism whereby the change gear train ratiocompensates for the bodily travel of the cutter during the rotation ofthe blank without requiring any auxiliary mechanism to effect thiscompensation.

Further objects are to provide a gear cutting machine having thecharacteristics hereinabove enumerated in which two change gear trainsare provided, one of which determines the rate of advance or .feed ofthe cutter and the other of which determines the pitch of the teeth sothat the machine may be easily adjusted for any desired pitch and mayalso be easily djusted to secure the most advantageous rate of cuttingfor the particular material of which the gear blank is formed.

An embodiment of the invention is shown in the accompanying drawings, inwhich:

Figure 1 is a rear end view of the machine.

Figure 2 is a plan view thereof.

Figure 3 is a side view of the machine from the left-hand side of Figure2.

Figure 4 is a front end view of the machine.

Figure 5 is a diagrammatic view showing the gear train drives for theseveral parts of the machine,

Figures 6 and '7 show gear trains which may be used interchangeably withthe gear trains shown in Figure 5.

Figure 8 is a fragmentary view corresponding approximately to a sectionon the line 8--8 of Figure 2.

Figure 9 is a detail view showing a supporting means that may beemployed for supporting one of the gears of a gear train.

Figure 10 is a view showing the relation of the cutter to a gear blank.

Figure 11 is a face view of a cutter.

Figure 12 is a diagrammatic View showing the face of a gear blank with asingle slot between gearteeth drawn in the position it wouldapproximately occupy to show the slight deviation from a perfectlycircular tooth slot.

Referring to the drawings, it will be seen that the machine comprises abody portion or bed I provided with a tailstock indicated generally at 2and a headstock indicated generally at 3. The headstick is adapted toreceive and drive an arbor or mandrel 4 upon which the gear blank 5 ismounted. The mandrel A is driven from a worm wheel 6. A cutter assemblis mounted in front of the gear blank, asshown in Figure 2, and maycomprise a frame or supporting portion 1 which a is supported from aslide 8. The slide 8 may be moved towards or from the gear blank bymeans of thescrew 9 operated by a hand Wheel 10 so that the cutter headll may be initially moved into its correct position for the particularsize of gear blank to be cut. Thereafter this adjustment towards or fromthe gear blank is not varied during the entire cutting operation.

The cutter head ll may comprise a disk as shown'in Figure 10, which isremovably carried by the shaft 2| in any suitable manner not shown, andremovably receives the cutting tools l3 and I4. These cutting tools havestraight cutting edges. The cutting edges for the tool [3 are indicatedat I5 and I6 and the cutting edges for V the tool I4 are indicated at I!and I8.

The mechanism is so arranged that the cutter head rotatesin thedirection indicated in Figure tioned below the gear as shown in Figure1, and

during the cutting operation the cutter rotates as indicated in Figure 1and the cutter assembly slowly rises, the cutter, however, remaining inthe same vertical plane during the entire operation. The gear blank 5 isrotated so that its face presented towards the cutter is travelingdownwardly and the cutter, therefore, cuts out the substantiall circularteeth, one of the slots being indicated by the reference character IS inthe diagrammatic view shown in Figure 12. V

The teeth are not exact circles for the reason that the peripheral faceof the gear blank adjacent the cutter is traveling downwardly, while onone lateral side the tools of the cutter are traveling upwardly and onthe other lateral side the tools of the cutter are traveling downwardly,and there is thus a slight difference in the relative velocity of thegear blank and the tools where they engage the gear blank on oppositelateral sides thereof. Additionally there is the low upward travel ofthe cutter assembly during the cutting operation, which also causes aslight deviation from a true circle for the teeth. As a consequence ofthis, the two meshing gears are cut so that their teeth arecomplementary. This is accomplished by reversing the direction ofrotation of the cutter 4 while maintaining the same direction ofrotation of the gear blank. Of course, the cutting edges of the toolsfor cutting the complementar teeth are on the opposite side from thatshown in Figure 10 as the direction of rotation of the cutter head hasit cuts all of the teeth completely around the gear blank due to therotation of the gear blank and;

the slow rise of the cutter head. This cutting is gradual and all of theteeth are cut completely around the gear blank to progressivelyincreasing depth as the cutter head rises and passes across the gearblank from a position below the blankto 'a position above the blank.While the direction of travel of the cutter head has been described asfrom below to a position above the gear blank, it is obvious that thecutter head could travel from above to a position below the gear blank.It would be preferable under these conditions tb reverse the rotation ofthe gear blank. 7

The entire mechanism may be driven from a single reversible electricmotor 20 which is mounted on the support or frame 1 and forms a portionof the cutter head assembly. Through reduction gearing, as shown inFigure 5, the motor 20 drives the, cutter shaft 2|; The 'end of thecutter shaft 2| is provided with abevelgear 22 which meshes with a bevelgear 23 splined on a slotted vertical shaft 24, see Figures 3 and 5, thebevel gear 23 being held by a suitable bracket as indicated in Figure 3andtraveling upwardly or downwardly with the cutter head assembly. Themeans for guiding the cutter head assembly for its vertical motion maycomprise a vertical guide 25 forming a unitary structure with the slide8. The support 1 is guided by the guide 25 and is moved directlyupwardly or downwardly by means hereinafter described. 7 I f Thevertical shaft 24 carries a bevel gear '26 which meshes with the bevelgear 21 splined on a slotted horizontal shaft 28; The bevel gears 26 and21 travel with the slide 8, see Figures 3 and 5.

The shaft 29, see Figure 5, is driven by change gear mechanism indicatedgenerally at 30, the end gears being removably carried by the shafts 28and 29 and the intermediate gears being carried in any suitable andconventional manner, as by means of the adjustable slotted links orsupports 3| which are removably and adjustably locked to the bodyportion by means of bolts 32, see Figure 9. Any other conventional wayof carrying the intermediate gears of the change gear train can beemployed.

It is obvious that when the direction of rota.- tion of the cutter headis reversed with reference to the gear blank by reversing the directionof rotation of the motor 20, that a different number of intermediategears have to be carried in are employed, whereas upon reverse directionof rotation of the cutter head, a different number of intermediate gearsare employed in-the change gear train as indicated at 33 in .Figure 7..In the case chosen for illustration, an odd number of gears 'is' shownin Figure 5 and an even number of intermediate gears is shown in Figure'7. This arrangement causes the gear blank to rotate in the samedirection although the direction of rotation of the cutter head has beenreversed.

The shaft 29 carries a worm 34 which drives the worm wheel 6, seeFigures '1 and 5.

The slide 8 is provided with a pair of upstand-- ing lugs 35,'-seeFigure 8, between which a worm wheel 36 is mounted. This worm wheel isslidably splined on the shaft 29 and drives a worm wheel 31. The wormwheel 3! drives the shaft 38 carried by the slide 8, see Figures 2 and-5. The drive from the worm wheel 31 to the shaft 38 is through theintermediate change gear train 39. If desired, any of the change geartrains 3-0, 33 or 39 may take the form shown diagrammatically in Figure6 and indicated generally by the reference character 46. In other words,the change gear trains may have intermediate ears provided with arelatively large gear and a relatively smaller pinion rigid therewith asone portion of the intermediate gear train in accordance with the wellknown practice, and also it is obvious that any of the intermediategears may be carried as indicated in Figure 9 wherever desirable.

The shaft 38 is provided with a worm M which drives a worm wheel 42rigid with a vertical screw 43, see Figures 1,, 2, 3 and 5. The screw 43is arranged vertically and elevates the cutter assembly in a gradual anduniform manner while the machine is in operation.

The operation of the apparatus is briefly as follows:

The gear blank 5 is mounted on the mandrel 4 and the cutter assembly isadjusted inwardly by means of the hand Wheel l and screw 9 until theteeth of the cutter head H are positioned in their correct relativespacing from the axis of the gear blank. At this time the cutterassembly is in a position below the gear blank. The appropriate geartrains are selected. The gear train 39 determines the rate of upwardfeed of the cutter head. Obviously, if the material is relatively hard,the upward rate of feed is slower than where the material is relativelysofter. The factor which determines the rate of cutting will, of course,be similar to that which would determine the rate of cutting on a latheor planer, namely, the surface speed and depth of cut of a tooloperating on the particular material. For instance, the number ofrevolutions of the cutter may vary from 80 to 300 R. P. M. depending onthe size of the cutter and the kind of material operated on. The speedis determined solely by the surface speed of cutting and the amount ordepth of each cut of a tooth is determined by the rate of upward feed.When this has been determined, the proper gear train 3.9 can be chosen.The gear trains .30 and 33, Figures and '7, are selected after the rateof feed has been determined and in conjunction with the gear train 39.For any given setting of the ear train 39, the selection of the geartrains 30 or 33 determines the pitch of the teeth out on the gear blank.

It is obviou that inasmuch as the cutter assembly rises upwardly at acertain predetermined rate, depending on the selection of the gear train39, that some means must be provided for compensating for the upwardtravel of the cutter assembly during the cutting operation. For exery ininches at the pitch line.

6 ample, if P equals the pitch of the teeth to be cut measured at thepitch line, and T equals the number of teeth, then P T equals theperiph- Assume that .F

equals the distance of vertical travel. of the cutter for one revolutionof the blank. Then is equal to the number of revolutions of the blankwhile the cutter travels a distance equal to the periphery of the blank.

It is apparent, therefore, that a correction factor must be interposedin the gear train 30 or 33 or, in other words, the gear train 30 or 33is so selected that one revolution less than the number of revolutionsof the blank is imparted to the blank while the cutter travels adistance equal to the periphery of the blank. This may be written asfollows:

It is therefore apparent that the gear train 30 or 33 must be correctedby the factor or correction ratio To express this matter in other words,it is apparent that the total number of revolutions of the gear blankduring the time that the cutter has traveled a vertical distance equalto the periphery at the pitch line of the gear blank is one less thanthe total number of revolutions of the gear blank, which would benecessary had the cutter stood still Without any vertical risewhatsoever.

This invention, therefore, provides a very simple means of obtainingthis result and it is secured without the use of any differentialgearing or other complicated means, for example as has heretofore beenemployed in my prior Patent No. 1,456,240 of May 22, 1923 for Gearcutting machine.

In View of the fact that the number of teeth on the individual gears ofthe gear train 30 or 33 are necessarily whole numbers, it is apparentthat it may become necessary to slightly alter the gear train 39 forcertain pitches and for certain numbers of teeth to be cut on a gearblank. In view of the fact that there is a material range of speed ofcutting that is permitted for any given material, it is obvious thatthis slight change in the gear train 39 may be made and still thecutting speed may be in the optimum zone of cutting speeds for theparticular material of which the gear blank is composed, but this slightadjustment of the gear train 33 will obviously vary the value of F inthe above formula and thus enable an operator to select the appropriategears for the gear train 30 or 33.

It is apparent from the above description that a very simple type ofgear cutting machine and a very simple method of cutting substantiallycircular teeth has been provided by this invention in which accuratemeshing of the drive and driven gear cut by this machine is obtained bycutting the complementary teeth, as has been detailed hereinabove.

Also it will be seen that thi machine enables the operator to rapidlycut the gears, for it is apparent that the cutter head may rotate at :ahigh rate of speed, being limited solely by the surface speed of thecutter teeth for the particular material chosen for the gear blank. Alsothis high speed is obtained due to the fact that there is no reversal ofparts, that is to say, there is no sudden stopping and starting of thecutters, as in my above noted prior patent. Instead of this, the cutterhead rotates uniformly, the gear blank rotates uniformly, and the cutterassembly rises at a uniform rate, and thus high speed operation isobtained. 7

' It will be seen further that the extreme simplicity of the machineenables it to be cheaply manufactured and also the construction of themachine is such that it may be ruggedly made, as the machine is freefrom complicated or delicate parts. Additionally, it is to be noted thatthe cutter tools themselves are easy to make as all of their cuttingedges are straight.

Although this invention'has been described in considerable detail, it isto be understood that such description i intended as illustrative ratherthan limiting, as the invention may be variously embodied and is to beinterpreted as claimed.

[I claim:

1. A machinefor cutting substantially circular teeth on gears which areadapted to mesh with the substantially circular teeth of one gear formedas complements of the substantially circular teeth of the other gear,said machine comprising blank rotating means, a rotary cutter, means forbodily moving the cutter in a plane parallel to the axis 'of rotation ofthe blank while the blank executes a large number of revolutions,'meansfor rotating the cutter and the blank and for reversing the relativedirection of rotation of the cutter and the blank for cuttingcomplementary teeth, said last mentioned means including a changegear-train whose ratio compensates for the bodily travel of the cutterby rotating said blank at a rate to produce during the bodily travel ofsaid cutter through a distance equal to the pitch circumference of thegear being cut a total number of revolutions of said blank differing byone from the number of revolutions of said blank which would haveoccurred had there been no bodily motion of the cutter.

2. A machine for cutting substantially circular teeth on gears which areadapted to mesh with the substantially circular teeth of one gear formedas complements of the substantially circular teeth of the other gear,said machine, comprising blank rotating means, a rotary cutter, meansfor bodily moving the cutter in a plane parallel to the axi of rotationof the blank while the blank executes a large number of revolutions,means for rotating the cutter and the blank and forreversing therelative direction of rotation of the cutter and the blank for cuttingcomplementary teeth, said last mentioned means including reversiblepower mean and including a change gear train whose ratio compensates forthe bodily travel of. the cutter by rotating said blank at a rate toproduce during the bodily travel of said cutter through a distance equalto the pitch circumference of the gear being cut a total number ofrevolutions of said blank differing by one from the number ofrevolutions of said blank which would have occurred had there been nobodily motion of the cutter.

3. A machine for cutting substantially circular teeth on gears which areadapted to mesh, with the substantially circular teeth of one gearformed .rotating means, a rotary cutter, means for bodily moving thecutter in a plane parallel to the .axis of rotation of the blank whilethe blankiexecutes a large number of revolutions, means for continuouslyrotating the cutter at a uniform rate of speed and for continuouslyrotating the, blank at a uniform rate of speed for one gearand forreversing the .relative' direction of rotationof the cutter and theblank for cutting the complementary gear, said last mentioned meansincluding a change gear train whose ratiocompensates for the bodilytravel of the cutterby rotating said blank at arate to produce. duringthe bodily travel of said cutter through a distance equal to the pitchcircumference of the gear being cut a total number of revolutions ofsaid blank differing by'one from the numbernof revolutions of said blankwhich would have occurred had there been no bodilymotion of the Acutter. 1

4. A machine for cutting substantially circular teeth on gears which areadapted to mesh, with the substantially circular teeth of one gearformed as complements of the substantially circular teeth of the othergear, said machine comprising blank rotating means, a rotar cutter,means for bodily moving the cutter in a plane parallel to. the axis ofrotation of the blank while the blank executes a large number ofrevolutions, means for con tinuously rotating the cutterat a uniformrate of speed and for continuously rotating the blank at a uniform rateof speed for one gear and for reversing the relative direction ofrotation of the cutter and the blank for cutting the complementary gear,said last mentioned means including reversible power means and includinga change gear train whose ratio compensates for thebodily travel of thecutter by rotatingjsaid blank at a rate to produce during the bodilytravel of said cutter through a distance equal to the pitchcircumference of thegear being cut a total number of revolutions of saidblank differing by one from the number of revolutions of said blankwhich would have occurred had there 7 been no bodily motion of thecutter. e

5. A machine for cutting substantially circular gear teeth comprisingmeans for rotating a gear blank, a rotary disk like cutter, means forrotat- 7 ing said disk like cutter aboutan axis at right angles to saiddisk like cutter, said disk like cutter having a plurality of teethprojecting oute wardly from said disk like cutter and approximatelyparalleling the axis of rotation of said disk like cutter, means forbodily moving the cutter in a plane parallel to the axis of rotation ofthe blank in a continuous manner while said blank is continuouslyrotating at a uniform rate such as to produce during said bodilymovement of the cutter through a distance equal to the pitchcircumference of the gear being cut a't'otal number of revolutions ofsaid blank differing by one from the total'number of revolutions of saidblank which would have occurred had there been no bodily movement ofsaid cutter, and means for varying the rate of feed of said disk likecutter.

6. A machine for cutting substantially circular 7 gear teeth comprisingmeans for rotating a gear angles to saiddisk like cutter, said disk likecutter having a plurality of teeth projecting outwardly from said disklike cutter and approximately paralleling the axis'of rotation of saiddisk like cutter; means for bodily moving the cutter ina plane parallelto the axis of rotation of the blank in acontinuous manner while saidblank is continuously rotating at a uniform rate such as to produceduring said bodily movement of the cutter through a distance equal tothe pitch circumference of the gear being cut a total number ofrevolutions of said blank difiering by one from the total number ofrevolutions of said blank which would have occurred had there been nobodily movement of said cutter, and adjusting means for selecting theparticular plane along which said disk like cutter will move.

'7. A machine for cutting substantially circular teeth on gear blankscomprising a body portion, means for rotating a gear blank, a slidecarried by said body portion, adjustable means for moving said slidetowards and from said gear blank, a right angle guide carried by saidslide, a rotary cutter adjustably supported from said right angle guide,means for continuously rotating said cutter, and means for continuouslymoving said outter with reference to said right angle guide while saidgear blank continuously rotates at a uniform rate such as to produceduring said bodily movement of the cutter through a distance. equal tothe pitch circumference of the gear being cut a total number ofrevolutions of said blank differing by one from the total number ofrevolutions of said blank which would have occurred had there been nobodily movement of said cutter.

8. A machine for cutting substantially circular teeth comprising a bodyportion, means supported from said body portion for rotating a gearblank continuously at a uniform rate, a guide formed on said bodyportion, a slide carried by said guide and adapted to be moved towardsand from said gear blank, a vertical guide carried by said slide, acutter assembly guided by said vertical guide, elevating means forraising said cutter assembly, said cutter assembly including a cutter,and power means for rotating said cutter and said gear blank and forvertically moving said cutter assembly a linear distance equal to thepitch circumference of the gear being out while the blank executes atotal number of revolutions one less than the number of revolutions ofthe blank which would have occurred had there been no bodily movement ofthe cutter.

9. A machine for cutting substantially circular teeth comprising a bodyportion, means supported from said body portion for rotating a gearblank at a uniform rate, a guide formed on said body portion, a slidecarried by said guide, manual means for adjusting said slide towards andfrom said gear blank, a vertical guide carried by said slide, a cutterassembly guided by said vertical guide, elevating means for raising saidcutter assembly, said cutter assembly including a cutter, and powermeans for rotating said cutter and said gear blank and for verticallymoving said cutter assembly a linear distance equal to the pitchcircumference of the gear being out while the blank executes a totalnumber of revolutions one less than the number of revolutions of theblank which would have occurred had there been no bodily movement of thecutter.

10. A machine for cutting substantially circular teeth on gear blankscomprising means for revolubly supporting a gear blank and forcontinuously rotating said gear blank at a uniform rate, a cutterassembly movable towards and from said gear blank, guiding means forguiding said cutter assembly for vertical motion, elevating means forraising and lowering said cutter as sembly, said cutter assemblyincluding a revolubly mounted cutter, power means for rotating saidcutter, a change gear train operatively positioned between the supportfor said gear blank and said revoluble cutter, and a change gear traindriven from said power means for vertically moving said cutter assemblya linear distance equal to the pitch circumference of the gear being outwhile the blank executes a total number of revolutions one less than thenumber of revolutions of the blank which would have occurred had therebeen no bodily movement of the cutter.

11. A machine for cutting substantially circular teeth on a gear blankcomprising a main body portion, means supported from said body portionfor revolubly supporting a gear blank, a longitudinally extending shaftgeared to the gear blank supporting means for rotating said gear blanksupporting means, a slide carried by said body portion and adjustabletowards and from said gear blank, a vertical guide carried by saidslide, a cutter assembly guided by said vertical guide, elevatingmechanism for said cutter assembly, change gear mechanism carried bysaid slide and operatively connected to said shaft irrespective of theposition of said slide, said cutter assembly including a revolublecutter, power means carried by said cutter assembly for rotating saidcutter, and change gear mechanism connecting said power means and saidrevolubly mounted cutter with said shaft.

FRANK W. JURY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 858,081 Liggett June 25, 19072,059,613 Schellens Nov. 3, 1936 1,709,835 Bottoher Apr. 23, 1929FOREIGN PATENTS Number Country Date 331,973 Great Britain July 17, 1930

